The present invention relates to systems and methods for processing multiple sources, and more particularly to separating the sources using directional filtering.
There may be instances in which there are several sources emitting signals. The combination of these sources typically forms a composite signal (e.g., a signal representing a mixture of these sources) that may be received by a sensor. While there are many applications for the received composite signal, such as amplification, it is sometimes desirable to selectively isolate or separate sources in the composite signal. This problem of separating sources is sometimes referred to as the “cocktail party problem” or “blind source separation.”
For example, in an acoustic environment, hearing aids may be used to amplify sounds for the benefit of the user. However, because hearing aids receive all sound impinging on its receiver, it amplifies desired sounds (e.g., conversation) and undesired sounds (e.g., background noise). Such amplification of all received sounds may make it more difficult for the user to hear. Therefore, hearing aids have been designed to filter out background noise (e.g., undesired sources) while allowing speech and other sounds (e.g., desired sources) to pass through to the user. One way to accomplish this is to separate the sources of sound being received by the hearing aid, reconstruct the desired sources, and transmit the reconstructed sources to the user.
As another example, source separation may be used to separate radio signals being emitted by different transmitters.
Several approaches have been undertaken to separate sources through the use of machines, mathematical models, algorithms, and combinations thereof, but these approaches have achieved limited success or are bound by restrictive operating conditions. Some approaches require use of multiple sensors (e.g., microphones) in order to separate sources. Such an approach relies on the relative attenuation and delay from each source as received by the multiple sensors. Use of multiple sensors is described, for example, in U.S. Pat. Nos. 6,526,148 and 6,317,703. Although these multiple sensor techniques may be used to separate sources, they fail when used in connection with a single sensor.
Single sensor source separation techniques have been attempted, such as those described in the Journal of Machine Learning Research (hereinafter “JMLR”), Vol. 4, 2003, and in particular, pages 1365-1392, and in Advances in Neural Information Processing Systems (hereinafter “ANIPS”), Vol. 13, 2001, and in particular, pages 793-799, but these techniques require detailed knowledge of the sources and fail to use directional filtering as a cue in performing source separation.
While existing machine/algorithm combinations strive to achieve source separation, organisms on the other hand, such as mammals, have an innate ability to distinguish among many different sources, even when placed in a noisy environment. The auditory processing functions of an organism's brain separate and identify which sounds belong to which sources. For example, a person placed in a noisy environment may hear many different types of sounds, yet still be able to identify the source (e.g., the radio, the person talking, etc.) of each of these sounds.
Organisms accomplish source separation by localizing sound sources using a variety of binaural and monaural cues. Binaural cues can include intra-aural intensity and phase disparity. Monaural cues can include directional filtering. Directional filtering is typically performed by the organism's ears. That is, the ears “directionalize” sounds based on the location from which the sounds originate. For example, a “bop” sound originating from the front of a person sounds different from the same “bop” sound originating from the right side of a person. This is sometimes referred to as the “head and pinnae” relationship, where the head is the sensor and the pinnae is the location of the source. These differences in sound, depending on the location in which the sound source is located, are used as spatial cues by the organism's auditory system to separate the sources. In other words, the ears directionalize each source based on its location and transmit the directionalized (e.g., filtered) sound information to the brain for use in source separation.
Therefore, it is an object of the invention to provide systems and methods that overcome the deficiencies of the aforementioned source separation techniques and that utilize directional filtering to accurately and quickly separate sources.
It is another object of the invention to separate sources using just one sensor.